(1) Field of the Invention
The present invention relates to a method for clarifying aqueous salt solutions containing inorganic insolubles and possibly also organic components as contaminants. The method comprises the addition of flocculants and the supply of microbubbles to the solution by means of dissolved air for flotation.
(2) State of the Prior Art
Removal of inorganic insolubles from aqueous solutions can in some cases be obtained by simply adding a flocculant to the solutions and allowing insolubles to settle, whereupon a clear solution can be decanted. However, in most cases such simple methods will be too time consuming or inefficient with regard to clarity of the salt solution. Flotation might give increased removal of insolubles, but if these have a density close to that of the salt solution itself, efficient separation of insolubles will not be obtained. If the salt solution also contains organic contaminants, the clarification might be even more difficult.
In separation technology, several special methods are known, like dissolved air flotation and froth flotation for clarifying contaminated solutions. Thus from U.S. Pat. No. 4,790,944, a flotation process is known for removing oil wastes and suspended solids from waste water in the petroleum industry. The separation may be enhanced by the use of coagulating agents such as salts of iron, aluminium or calcium, or organic polyelectrolytes. The main features of this known process are, however, the combination of dissolved gas and a stream of induced gas.
Further, in Chemical Engineer's Handbook, R. H. Perry/C. H. Chilton, 5th Ed., Section 21, pages 65-67, froth flotation to treat metallic ores is described using different types of flotation agents, dispersants or deflocculants and frothers. Commonly used frothers are pine oil, creolytic acid, propylene glycol ethers and aliphatic alcohols.